marionettejs/backbone.marionette

Better error messages

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#2,795 opened on Oct 28, 2015

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discussionhelp wanted

Description

When I'm using Marionette, I'll occasionally make errors such as accessing a region that doesn't exist e.g.

var MyView = Marionette.LayoutView.extend({
  regions: {
    main: '.main-hook'
  },

  onRender: function() {
    this.showChildView('layout', someView());
  }
});

var view = new MyView();
view.getChildView('layout');

The exception I get comes from inside Marionette as a Cannot read property currentView of undefined or this.getRegion(..) is undefined. While I can chase the stacktrace back to find out the exact issue, it would be much better if I could get the following error:

LayoutError: 'layout' is not a region on MyView. The available regions are: 'main'

This is just to illustrate my point - if we have the information on why something isn't going to work we should tell the developer to save them time.

Contributor guide

Tech stack
javascript
Domain
frontend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
understanding of Marionette's region APIJavaScript debugging
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Examine the Marionette source code, likely in `src/marionette.view.js` or `src/region.js`, to understand how `showChildView` and `getRegion` work. The goal is to add a check in the region lookup method to detect when a region name is invalid and throw a custom `LayoutError` with the message format shown in the issue. Consider creating a helper function that lists available regions to include in the error message.
Better error messages · marionettejs/backbone.marionette#2795 | Good First Issue